Nearly six hundred years into the future, mankind inhabits the space colony Astrobe and is down to its third chance, after the Old World and the New World failed back on Earth. Though Astrobe is a utopia, devoid of crime, illness, poverty, etc., people are repulsed by their lives and have taken to migrating into a kind of ghetto, called Cathead, where they toil in oppressive conditions until they die early. Desperate for a leader who can save their world, the powers behind the throne transport Thomas More to their time, because they are impressed by the one truly honest moment that led to his martyrdom. They expect to be able to manipulate him, as a mere figurehead, not least because their society resembles the one he called for in his Utopia.

A bizarre decision that, given that he'd lost his head precisely because he refused to be used in that fashion. And, sure enough, he's no more amenable to being a puppet this time around. He is attracted by the good that the system of Astrobe has achieved, but comes to see that it ultimately dehumanizes life too thoroughly to satisfy its citizenry and inevitably leads to even the extreme measure of seeking freedom at the cost of one's comfort and life in the Cathead. Thus begins his march to his next martyrdom.